Caprella angusta Mayer 1903

Length: 10.8mm. Head with median triangular anteriorly pointing spine; pereonites may be smooth or may have small paired dorsal tuberculations, particularly posteriorly. Antenna 1 as long as or longer than cephalon plus pereonite 2; antenna 2 longer than antenna 1 peduncle, flagellum with short setae. Gnathopod 1 with serrate grasping margin to propodus and dactylus. Gnathopod 2 propodus twice as long as it is broad, palm with proximal poison spine with small proximal accessory spine, triangular or rectangular projection distally; some setae on palm. Dactylus thickened proximally, tapered distally, grasping margin denticulate. Basis attached anterior to middle of pereonite 2, having antero-lateral ridge. Gills fat, oval. Pereopods 5 to 7 increasing in length, propodus palm concave, grasping spines proximal. Females differ in having gnathopod 2 attached anteriorly, with small propodus bearing proximal grasping spine and accessory spine and evenly tapered dactylus.

California, Oregon, Washington, British Columbia

Caprellid, “Ghost” or “Skeleton” shrimps, so called for their skeletal appearance. Amphipod crustaceans, easily distinguished by the elongate stick-like body form and reduction of the abdominal appendages. Head is generally fused with pereonite 1. Pereopods on first 2 segments (pereonites) are most flexible and called gnathopods; gnathopods 2 being the largest, used in defense, feeding and substrate attachment. In many species pereopods 3 and 4 may also be reduced or absent. Gills on pereonites 3 + 4, rarely on pereonite 2. Pereopods 5 - 7 much smaller than 1 + 2, used for clinging to the substratum. In females, brood plates (öostegites) develop on pereonites 3 + 4. Much remains to be learnt about their biology, ecology and in many cases changing distributions.

Tentatively assigned to C. penantis by McCain (1968) but Laubitz (1970) considered them to differ sufficiently and gives guide to their differences. Described to be the same as C. natalensis by Martin 1977. National Museum of Natural History (NMNH) specimens labeled as C. acutifrons by J. McCain. Specimens in samples vary in morphology, only distinct similarity is short head spine (G. Ashton pers obs).

C. angusta, C. incisa and C. verrucosa are all members of the ‘acutifrons’ group, typically similar in their general body shape, the shape and armature of the second gnathopods, and the proportions of the antennae. C. angusta is typically the smoothest, and C. verrucosa with the most extreme large blunt spines. C. incisa can be distinguished from C. verrucosa by its much smaller tuberculations, finely setose antenna 1 and very large propodus and antero-lateral ridge on gnathopod 2. C. angusta can be distinguished from C. incisa by its almost smooth dorsal surface, normal sized gnathopod 2 propodus and basal ridge, anterior attachment of gnathopods 2, absence of pleura and of setae on antenna 1. See Laubitz 1970 for table comparing these species.

National Museum of Natural History, Washington DC: (NMNH) 120848

How to Distinguish from Similar Species: Tritella pilimana has a vestigial pereopod on pereonites 3 and 4, while Caprella angusta does not. Several other members of genus Caprella either do not have the large triangular spine on the dorsal side of the head, or also have large dorsal tubercles on their pereonites and gnathopod 2 is attached near the middle of pereonite 2.

This freeliving caprellid amphipod has gills on only pereonites 3 and 4. It has no pereopods on pereonites 3 and 4. Gnathopod 2 has a propodus which is less than 2/3 as wide as it is long, and the propodus of pereopods 5-7 has only one grasping spine or tooth. There is no spine on the ventral body surface between gnathopods 2, but there is a large, dorsal, anteriorly directed triangular spine on the back of the head. It has few or no tubercles on the dorsal surface of the pereonites, and none on pereonite 1. Gnathopod 2 of the male is attached at the anterior end of pereonite 2.

Biology/Natural History: Caprellid amphipods such as this species are roving predators. We often find them climbing on eelgrass or hydroids searching for prey. With their large claws and bizarre shape they would truly be monsters if they were our size!

Caprella angusta er en art i slekten Caprella innenfor spøkelseskreps-familien (orden Caprelloidea eller «spøkelsestanglopper») - en type tanglopper. Larvene er planktoniske. De er relativt små, med to store ot to små antenner. De lever bare i havet (saltvann), og er utbredt i farvannene ved vestkysten av USA og Canada.

Arten er 11 mm lang. Den ble oppdaget under Siboga-ekspedisjonen.